Known in the art are electronic circuits for generating fuel injection control pulses in which a capacitor is charged at a rate depending on the magnitude of some operational variable. In a second time interval and after the occurrence of a trigger pulse, the time required to discharge the capacitor is used to determine the duration of the fuel injection time. After the capacitor is discharged, the system rests until the occurrence of the subsequent charging cycle. The charging and discharging cycles follow one another sequentially. It is an inherent disadvantage of the known system that, while the capacitor is discharging and while the system is in its rest phase, the voltage across the capacitor is not related to the magnitude of the operational control variable of the engine. Accordingly, the system does not have available a continuous control variable.